We had a guide make "river coffee" for us one morning camping on the Penobscot River in Maine. (We were on a multi-day white water trip, first day included some Class V rapids, and we all needed something to kick us into gear for day 2.)
-ground coffee is dumped into a boiling pot of water on the campfire coals and cooks for a while
-the pot is removed from the heat, sits for a minute so the grounds settle to the bottom.
-an egg is cracked into the pot, which settles to the bottom, and "cooks" the grounds in place
-carefully, you pour off the liquid into your cup, mostly the gounds stay in the egg

It's strong, powerful stuff, perfect for kicking off a day on the river. (The first few cups are best, the last couple are a little scary)